1. Field of the Invention
This invention relates to an apparatus for polishing interior surfaces of pipes, and more particularly to an apparatus for polishing inner surfaces of pipes of relatively small inside diameters.
2. Description of the Prior Art
It is known in the art to polish interior surfaces of a pipe which is horizontally supported on a support table and rotatably gripped at opposite ends thereof for rotation in one direction. An inner polisher rod which is inserted into the pipe throug one end thereof is rotated in a direction reverse to the pipe rotation direction, and polishing grains are injected into the gap between the inner surface of the pipe being treated and the polisher rod to polish the interior surfaces of the pipe.
FIG. 1 illustrates one example of such pipe polishing apparatus, supporting pipes 1 horizontally on a support table 2. Mounted on a movable frame 3 are grippers 4 which releasably grip one end of the pipes 1 and polishing grain injection pipes 5. Frames 3 are movable toward and away from the pipes 1 by operation of a transfer mechanism 6. A fixed support frame 7 which faces the other ends of the pipes 1 is provided with second grippers 8. When the movable support frame 3 is pressed against the pipes to be treated, opposite ends thereof are securely gripped in the respective grippers 4 and 8 to rotate the pipes 1 by a motor 9. Designated by 10 is a box for collecting the polishing grains. Inner polisher rods 11 are retractably inserted into the respective pipes 1 by a reciprocable feed mechanism 12 and rotated by a motor 13 in a direction opposite that of the pipe rotation.
During the polishing operation by the apparatus of this sort, it is often experienced that the pipe 1 undergoes excessive abrasion at the end opposite to the polishing grain injecting end (P) or at the polishing grain discharging end (Q) as indicated by reference number 14 in FIG. 2, which is generally referred to as "bell mouth." The bell mounth phenomenon usually occurs over about 1/3 of the lengths of the treated pipes.